Process of making heavy fuel oil



March l1, l1941.

E W. THIELE aoctss or mma HEAVY FUEL on.

Filed on. 19. 193e' |NvENToR Ernest W Tele over@ ATTORNEY www lak

`V Quik YPatented Manll, 1941 UNITED STATES PROCESS MAKING HEAVY FUEL OIL Ernest W. Thiele, Chicago, Ill., assigner to Stamiard Oil Company, Chicago, lll., a corporation oi.'

' Indiana Application October 19, 1938, Serial No. 235,823

Claims.

This invention relates to the conversion of hydrocarbon oils and particularly to the thermal conversion or pyrolysis oi.'l heavy hydrocarbon oils I into gasoline. One object of theinvention is to 5 convert hydrocarbon oils, particularly intermediateboiling oils of the type of gas oils, into gasoline and fuel oil in a manner to produce gasoline of high Aknock-rating and more valuable fuel oil of lower viscosity than heretofore produced by cracking processes. However, the-process may be operated to give higher yields of gasoline of a knock-rating comparable to that now ordinarily produced. A specific object of the invention is to produce improved heavy fuel oil as a by-product of gasoline obtained by the cracking of mixed base gas oil, said heavy fuel oil having a high heating value combined with a low viscosity and a low pour point.

It has heretofore been proposed to separate heavy hydrocarbon oils into fractions by distillation and then separately convert the fractions. It has also been proposed to separate oils into fractions by the action of solvents. According ple Mid-continent gas oil, is subjected to solvent extraction, thereby separating it into an extract fraction consisting essentially of aromatic hydrocarbons, and a rainate fraction comprised of non-aromatic hydrocarbons. The raffinate fraction is then subjected to conversion at an elevated temperature, producing gasoline and a very l heavy `substantially non-volatile fuel oil whose characteristics make it unsuitable for general use. This fuel oil is then blended with the extract obtained from the original gas oil, whereupon a fuel oil is obtained having the desired characteristics, especially the desired viscosity.`

to the present invention, a heavy oil, for exam' gravity and of the following A. S. T. M. distillation:

' F. Initial 478 10%-- y511 5 20%-; 530 30% 543 40%" 556 5o`%- 57o- 6o% 586 1 604 628 670 End point '732` l5 Various solvents may be employed for the extraction such as aniline, nitrobenzene, liquid sulfur dioxide, phenol, monochlorophenol, furfural and other oxygen or halogen containing organic solvents. The operation of tower Il 20 may be improved by introducingI the feed stock through line l0 at a slightly elevated temperature, for example, to 150 F. with nitrobenzene and simultaneously apply cooling means, not shownl to either or both ends of the tower, '25 thus causing a separation of oil from solvent in the end zones which results in a refluxing and fractionating action. The solution of solvent and extracted material is withdrawn from the bottom of tower Il by line Il leading to extract still Il 30 where the solvent is distilled oi and recycled by l line I5 to condenser I6 and solvent receiver I1 whence it ilows by pump I8 andline I9 back ,to the extraction tower Il. 'I'he extract oil substantially free of solvent is withdrawn by line 20 .35 for use as yhereinafter described. The amount of extract separated depends on the character of the gas oil charged to the extraction tower Il'. It will vary within the range of 5% to 30% and usually will fall within the range of 7% to 15%. The raffinate or gas oil fraction undissolved by the solvent is conducted by line 2| to ramnate stlill 22 wherein solvent is distilled olf by line 23 and the raffinate substantially free of solvent is 45 conducted by line 24 and pump 25 to cracking furnace 26. Here the oil is heated to a. highl temperature within the cracking range, e. g. 900 to 1100 F. whereby a substantial part of it is converted to gasoline and other light hydrocar- .50

`the raffinate oil which has been treated with the `solvent will crack at a higher rate so .that a higher `percentage of cracking per'pass through furnace. `26 is obtained than in the ca se of ordinary cracking stocks which have not been solvent treated. For example, at a single pass, I may convert 20 `to 40% of the gas oil charged to furnace 26, including the oil which is recycled, into gasoline having a boiling range of about F. initial tu 400 F. end point. The oil vapors from furnace 26 are conducted byline 21 to evaporator 28. If desired, additional cracking may be obtained by passing the hot vapors through soaking drum 2,9 before passing to evaporator 28.

` As a modification of my process, I may employ cracking catalysts, for example, by substituting Cin soaking drum 29 a catalyst chamber containing a suitable granular solid catalyst for effecting increased conversionof gas oil'into gasoline. Suitable catalysts for this purpose are fullers earth or bentonite clay, preferably acti.

vated by treating with acid, aluminum oxide,

preferably deposited on a suitable support such as kieselguhr or'silica gel, copper oxide, cadmium oxide, thorium oxide, etc. The oxides or hydroxides of these metals may be depositedon the silica by adsorbolysis, i. e. hydrolysis by adsorption. When employing a catalyst, it is necessary to regenerate it at intervals by blowing with air to oxidize carbonaceous material deposited thereon.

No heavy tar is produced by the catalytic cracking operation but .a refractory heavy oil is obtained which I may blend with the extract obtained from the feed stock to produce the desired fuel oil. Thus, when employing a catalyst in conjunction with cracking furnace 26, I may withdraw a. relatively light fuel oil from evaporator 28 byline 30 and blend it with extract in mixer 64, said extract being introduced by line 66 directly as obtained from the charging stock or by line 63 after it has been subjected to cracking. A cracking temperature of about 850 to 1000" F. is usually satisfactory for catalytic cracking and pressures ofthe order of 10 to 50 pounds per square inch may be employed. Gasoline obtained from the catalytic cracking operation has a higher anti-knock value than when no catalyst-is used. For example, it may have an octane number of 80 to 85 instead of 70 to 75 usually obtained without catalyst. In evaporator 28, suflicient cooling occurs to separate from the cracked vapors a very heavy residue or tar which is withdrawn by line 30. In

the case of non-catalytic cracking this tar will usually have a viscosity of about 400 to 1000 sec. `furol at 122 F., according to my process. The vapors are conducted by line 3| to fractionator 32 where all hydrocarbon constituents lheavier than the desired gasoline are separated and recycled to the cracking furnace 26 by line 33 and pump 34. Vapors or gasoline and'gases are conducted by line 35 to condenser 36 and thence to receiver 31. Uncondensed gases are eliminated from the system by line 38. The 'gasoline is then conducted by pump 39 and line 40 to stabilizer tower 4| where undesired gases are fractionated from the gasoline which is withdrawn'by line 42. The gases, consisting chiefly of propane and propylene, together with smaller amounts of C4 hydrocarbons, ethane .and ethylene, are withdrawn `by line 43, condensed in condenser 44 and co1'- lected in receiver 45. 'The liquefied gases from receiver 45 are withdrawn by pump 46 and lineV and at the same time it acts to cool the vapors and condense out the desired amount of residue or tar withdrawn by line 30.

A portion of the gas oil from line I0 may also be conducted to evaporator 28 by lines 50 and 49, the amount being `regulated to prevent over contamination of the solvent refined stockundergoing cracking therein. Raw gas oil thus introduced into evaporator 28 is partiallycracked and distilled therein and ultimately recycled by line 33 to cracking furnace 26, where it is mingled and cracked with rainate oil from 22.

The extract fraction of the gas oil charged to the system is withdrawn from still I4 by line 20 and forced by pump 5| to cracking furnace 52 Where it is rapidly heated to conversion temperatures of the order of 850 to 975 F. 'Ihe products of conversion are conducted by line 53 to -fractionator 51 wherein gasoline and lighter hydrocarbons are removed by vapor line 58 leading to condenser 59 and receiver 60. The condensate is then withdrawn from receiver 60 by pump 6| and line 62 leading to stabilizer 4| Where the desired gasoline is separated as hereinbefore described. The residuein the bottom of fractionator 51 is withdrawn by line 63 leading to fuel oil blending tower 64. The heavy products from evaporator 28 and fractionator 51 are combined in tower 64 to produce the desired fuel oil which is withdrawn from the tower by line 65. The viscosty 'of the very heavy tar from evaporator 28 is thereby reduced to the viscositydesired in the fuel oil. This may be regulated by withdrawing stock at 63a, by regulating the extractor Il to v give more or less extract or by passing more or less 1,stock through line 50. In addition, I may further reduce the viscosity of the tar from evaporator 28`and fractionator 51 by introducing a regulated amount of gas oil extract by line 66.

Heretofore attempts to crack gas oil charging stock extensively to produce maximum gasoline yields has resulted in the production of a tar of very high viscosity and low A. P. I. gravity. At the same time, extensive cracking has occasioned much difiiculty with coking of heater tubes. In order to make a satisfactory marketable fuel oil from the heavy tar, just mentioned, it has been necessary to blend it with lighter stocks which Were in themselves valuable as potential gasoline producing material. By my process, I select by solvent ext'raction'those constituents of the gas` oil charging stock which, because of their aromatic nature, produce little or no gasoline when subjected to cracking. rI then conduct the cracking operation in ysuch a manner that a very heavy tar is produced which is unmarketable as fuel oil and I combine this tar with the aromatic. extract previously separated to produce a fuel oil having a viscosity below 250 sec. furol at 122 F.

As an example, I may conduct the operation of 15 furnace 26 to produce a fuel oil in evaporator 28 having viscosity of 794 seconds furol at 122 F. and thereafter blend sufficient light fraction'by line 63 to reduce the viscosity to 175 sec. furol at 122 F., thus making it satisfactory for use in atomizing fuel burners. 'I'he 'amount of.light fraction from fractionator 51 required for reducing the viscosity to this extent is about 10%- A larger or smaller amount of the light fraction may be introduced, depending on the character of the fuel oil required. Thus, the blended fuel oil product may have a viscosity of 100 to 200 sec. furol at 122 F. It is generally desirable that the viscosity be less than 250 sec. furol at 122 F. The effect of combining extract from line 5S with tar from evaporator28 is shown by the following table:

j The pressure employed in the cracking' operations conducted in furnaces 26 and 52 may be varied over a considerable range, for example, from 50 tc 1000.pounds per square inch. However, I prefer to employ pressures of the order of.

400 to 150 pounds per square inch at the outlet of furnace 25 and 50 to A200pounds at the outlet of furnace 52, and reduce the, pressure. in evan; orator 28 and 'tower'i Vto between 50 and 200 pounds per square inch.

Although I have described' the recycling off liquefied normally gaseous 'hydrocarbons Y from receiverto cracking furnace 20, li may also employ gas reversion in cracking .furnace 52. For this purpose liquefied gases 'may .be conducted from pump by valved line 5ft to the inletoi the coil in furnace 52 wherein the liquefied gases, e. g. liquid propane or propylene, together with other liquefied gaseous hydrocarbons, such as ethane, ethylene, butane and butylene, react with the extracted oil from tower i t to produce higher yields of gasoline and reduce the tendency of the extract oil to produce coke in heater 52.

Although I have described my process with respect to certain embodiments thereof, I-intend that it be limited ing claims;

Iclaim: 1. The process. of converting gas oil cracking stock into gasolineandmerchantable 'fuel oil which comprises separating said gas oil vstock by the action of a 'selective solventinto a raffinate and an extract fraction, subjecting` the ramnate only as set forth in thel followfraction to cracking at a high cracking temperature between 900 and 1l00 F., separating the cracked products into heavy tar having a viscosity of about 400 to 1000 seconds fural at 122 F., cycle oil,gasoline and gaseous hydrocarbon constituents, recycling the said cycle oil to sai-d cracking operation and reducing the viscosity of said heavy tar by combining therewith a suffi--A cient amount of said extract vfraction to produce the desired merchantable fuel oil.

2. The process of converting heavy hydrocarbon oil stock into gasoline and heavy fuel oil which comprises separating said hydrocarbon oil stock b'y the action of a selective solvent into a raiiinate and an extract fraction, subjecting the raiinate fraction to cracking at a high cracking temperature between about 900 and -1100 F., ,separating the cracked products into heavy tar 4. In the process of converting gas oil into gasoline and a desirable fuel. oil having va viscosity below 250 sec. furol at 122 F, wherein the cracking operation is lconducted under conditions to produce a maximum yield of 'gasoline and concurrently atar oi viscosity above 250 sec. furol (122F.) for fuel oil, `thein'iprovement vcomprisinginitially sr-iparatins.:` said gas oil by means of a selective solvent into a rainate fraction and an extract fraction; cracking said railnate fraction at a temperature between about 900 and 1100 F., evaporating the cracked products to separate therefrom a tar having a viscosity above 400 sec. furol at 122 F., fractionab ing the desired gasoline from the remaining vapors and .recycling to said cracking operation intermediate boiling cycle oil and combining with said tar a regulated amount of said extract rraction to produce a fuel oil having a viscosity within the range of about 100 to 250 sec. furol at 122 F.

5. In the process of claim 4 the additional step' .of subjecting said 'extract fraction to once through cracking without recycling before combining it with said tar to produce said fuel oil having a viscosity within therange of about 100 to 250 seconds furol at 122 F. i

' ERNEST W. THIELE. 

